Subject: Re: My problems with merged memory
To: None <>
From: Michael L. Hitch <>
List: amiga-dev
Date: 03/07/1994 09:56:38
On Mar  7, 11:37am, Gregory Kritsch wrote:
> > >>>>> "Niklas" == Niklas Hallqvist <> writes:
> > 
> > Niklas> I have tested the board both with and without the DTACK jumper
> > 
> > I tried to decode it last night, and have now an idea of what it is
> > used for.  DaTa ACKnowledge is driven low as long as the requested data
> > is invalid, or if it were the opposite, in order to make slow memory
> > (or slow memory-mapped registers) safely deliver values to the CPU.
> > Is this correct?  I don't think the 16bit mem is to blame in this case
> NOTE: I only have access to Zorro I specs, but I don't imagine the A590
> would work with my A1000 if this stuff had changed...
> The docs I have suggest that DTACK* is generated by the motherboard for you,
> unless you assert the XRDY* pin (#18), in which case DTACK* will not be
> asserted until you negate XRDY*.
> > Niklas
> Hope this helps (and if the information HAS changed for Zorro II, would
> someone please let me know).

  A properly functioning Zorro II board shouldn't drive the DTACK* line,
but it might use it for timing.

  I've got some information from a post on comp.sys.amiga.hardware about
the HardCard+8 board and problems on older motherboards.  The article
indicated that J15 on the HC+8 board should be jumpered on motherboards
older that 4.5.  My board is something like 4.2, and I couldn't get the
memory on the HC+8 board to work at all until I put a jumper on J15.  The
article I have indicated that the jumper provided a pull-up resistor on
the DTACK* line.


Michael L. Hitch			INTERNET:
Computer Consultant			BITNET:  OSYMH@MTSUNIX1.BITNET
Office of Systems and Computing Services
Montana State University	Bozeman, MT	USA